Noninvasive angiography with magnetic resonance has recently been demonstrated in our laboratory. By manipulating the inherent sensitivity of MR to proton motion, blood flow generates its own contrast. The projective format provides images of the vascular tree that resemble conventional Roentgen angiograms. Preliminary results demonstrate high resolution vascular images. Flow volume quantitation has also been demonstrated. This work proposes to extend, validate and apply these novel techniques. Parameters that affect both image quality and flow quantitation will initially be investigated in-vitro. Results will be used in an iterative fashion to refine these sequences. Validation of these techniques will proceed in animal models of abdominal aortic aneurysm (AAA) and iliofemoral occlusive disease. Qualitative and quantitative MR results will be compared with contrast angiography and with invasive measures of flow volume. Studies will then be obtained in selected patients with AAA and iliofemoral occlusive disease. Similar qualitative and quantitative comparisons will be made which will assist in the development of appropriate clinical MR angiographic protocols. Finally, a prospective study will be performed comparing contrast angiography with optimized MR angiographic techniques. It is anticipated that MR angiography will develop into a valuable diagnostic tool that may obviate the need for more invasive procedures.